Counterbalance for instrument movement and pointer



Dec. 23, 1947. R. SIMPSON COUNTER-BALANCE FOR -IVI'IlUMENl MOVEMENT AND POINTER Filed March 2, 1944 Patented Dec. 23, 1947 COUNTERBALANCE FOR INSTRUMENT MOVEMENT AND POINTER Ray Simpson, River Forest, Ill. Application March 2, 1944, Serial No. 524,801 18 Claims. (Cl. 11G-136.5)

The present invention relates to counterbalances for instruments, and is particularly concerned with counter-balancing devices adapted to be used to counter-balance the moving element of electrical instruments, such as, for example, milliammeters, voltmeters, etc., of the moving coil type.

Some of the devices of the prior art have been subject to the inherent disadvantage that the adjustment of the Weights used causes friction and involves the application of a considerable force which may damage the pivots of the moving elements and reduce the life of the instrument.

Other devices of the prior art involve the use of very small nuts, which are difficult to manufacture and to fit to the balance arms, and also have a tendency to turn and become loose, thus getting out of position and throwing the movement out of balance.

Another disadvantage of the prior art devices is that, as many of these weights have to be removed and replaced with weights of another value on as many as thirty or forty percent of the instruments, the prior art devices involve much labor and time consumption in such replacements.

In doing this, when the instrument is completely assembled, great damage is often done to the pivots. The weights of the prior art devices also freeze in position and become difficult to move, thereby bringing about damage to the pivots, and special tools are necessary to fit them and to drive the-m in either direction on each of the balanced arms.

One of the objects of the present invention is the provision of an improved counter-balanced construction which does not require the bending of parts or the cutting of threads on the balance arm, and by means of which all adjustments can be made by merely sliding the weight back and forth or turning it slightly by means of a pair of tweezers, if a micrometer balance is desired.

Another object of the invention is the provision of an improved counter-.balance for instruments of the class described which is adapted to maintain its adjustment for a long period of time under the most adverse conditions of use, such as during jarring or vibration, and which is also adapted to be adjusted as desired by the application of a minimum amount of force, without damage to the parts of the assembled instrument.

Another object'of the invention is. the prQvSion of an improved form of counter-balance for instruments of the class described, which is peculiarly adapted to be removed very quickly and replaced with Vanother substitute, without the danger of damaging the pivots of the instrument, and without the tedious threading of the counterbalance on the balance arm.

Another object of the invention is the provision of an improved counter-balance for electrical instruments, which is not only adapted to be quickly applied or removed or adjusted .by a large increment, but which is also capable of a very minute or micrometer adjustment with the application of a minimum amount of force to the -moving element.

Another object of the invention is the provision of an improved counter-balance structure which isv simple, sturdy, capable of economical manufacture, and applicable to a wide variety of different instruments.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views,

Referring to the single sheet of drawings,

Fig. 1 is a top plan view of the moving element of a milliammeter equipped with counter-balancing weights embodying my invention;

Fig. 2 is a side elevational view of the structure shown in Fig. 1;

Fig. 3 is an end elevational view of the structure of Fig. 1;

Fig. 4 is an enlargediragmentary view of one of the smaller counter-weights carried by the laterally projecting balancing arms of the move- -ment of Fig. l;

Fig. 5 is an end elevational View of one of the balance arms equipped with a counter-balance and a retaining device embodying the invention.

Referring to Figs. l, 2, and 3, I0 indicates the moving element of an electrical instrument of the moving coil type, a fragment of the dial of which is indicated at II, and provided with scale divisions I2. The moving element Ill may include a hollow spool I3, which is substantially U-shaped in cross section, and which has a sub- `stantially rectangular 'central opening I4.

.The moving element;l I0 is provided with the usual hair springs, which serve the usual purpose of urging the pointer to its zero position and of conducting current through the moving coil of the instrument.

The exterior of the spool I3 supports themoving coil windings I5, which are connected to the terminals of the instrument by means of suitable connections through the springs carried by the moving element. At its top and bottom the moving element I is provided with the usual pivot members I6, suitably mounted in jewels and adapted to support the moving element for rotation about an axis located at the center of the pivots. At one end the moving element supports a cruciform member |1, which is provided with a tapered enlargement I8 carrying,A

the pointer arm 9, to which the sheet metal pointer 20 is attached.

The cruciform member I1 may have a circular body portion 2| and a plurality of radially extendingr balance arms 22, 23, 24. The member |1 is preferably made of sheet metal, and the thickness of the member |1 may be such that the balance arms 22-24 are substantially square in cross section.

The body 2| of the member l1 is iixedly secured to the moving element I1, 4and the balance arms 22 are provided with counter-balancing members 25, 2B, 21, which may be suitably adjusted on the arms 22--24 to approximate a dynamic balance of the moving element of the instrument 1.

The. counter-balancing members 25-21 are preferably relatively tight or closed coil helical spring members, and may be constructed of `any suitable metal, such as, for example, bronze. The pointer 2D and its supporting member I1 may be constructed of any suitable metal, such as, for example, aluminum, or other light metals or alloys.

The size of the helical coil spring members 25-21 is preferably such that the springs slide freely on the balance arms 22--24, but with a minimum amount of friction, but the length of the respective springs 25-21 depends on their location and upon the amount of adjustment desired, and the lateral arms 22-24 are preferably provided with shorter springs 25, 26, since there is a much lesser amount of weight and adjustment necessary, to counter-balance the movement in this direction, The counter-balance 21 onthe longer balance arm 23, which is opposite to the needle 20, is longer and heavier on account of the greater range of adjustment desired; and a greater amount of weight is needed to counterbalance the needle, which extends diametrically opposite to the arm 23.

The counter-balance members 25-21, which are slidably mounted on the balance arms, are preferably held in place by means of a plurality of resilient arms 28-30, these arms being located above each of the balance arms 22-24 and extending radially from a centrally located circular body 3|, which is carried directly above the body member 2|, which supports the balance arms 22-24 and the pointer arm Il.. The arms 28-30 and their supporting body are preferably made of resilient spring material, such as spring phosphor bronze.

The body 3| is also xedly secured to the Inoving element assembly I0 in such manner that the spring arms ZB-S extend parallel to the balance arms 22-24.

Each of the spring arms may be bent upwardly to provide an oiset portion 3.2 adjacent the body portion 3| so that the main portions of the spring arms are spaced slightly from the balance arms 22-24. At each end `of each spring arm the spring arm is preferably bent downwardly at substantially right angles, and downwardly bent por-v tions 33-35 are each provided with a beveled surface 36, preferably located on the inside so that the end of each of the downwardly bent portions 33-35 is provided with a relatively sharp knife edge 31.

The knife edge 31 engages between the successive coils of the springs, and the resilient action of each of the spring arms 28-30 also causes the coil spring to engage tightly against the two adjacent corners 38-39 of each of the balance arms so as to prevent rattling.

When it is desired to effect an adjustment or removal of one of the springs, a large adjustment may be made by merely prying the spring arm upward or away from its corresponding balance arm until the knife edge 31 is disengaged from the spring, when the spring will slide freely on or off the balance arm, or it may be adjusted longitudinally of the balance arm.

When the spring arm is released, it will imme diately bring its knife edge 31 into engagement with the counter-balance spring weight, and will cam the spring longitudinally until the knife edge settles in one of the tapered grooves 40 between the successive coils or turns of the spring.

Then a ne or closer adjustment of the spring longitudinally of the balance arm may be secured by merely rotating the spring on the counter-balance arm by means of a pair of tweezersV When the spring is rotated, the tapered grooves 40 between the coils of the spring will act like the grooves of a thread, and the outwardly projectlng rounded portions of each coil of the spring will act like threads, engaging the knife edge 31.

As the spring is rotated, it will necessarily progress along the arm a very small amount, and a very accurate adjustment of the position of the counter-balance weight may thus be secured.

It will thus be observed that I have invented an improved counter-balance structure, the weights of which may be adjusted by means of the application vof a minimum amount of force. Furthermore, it is unnecessary to make any very small threaded members or to cut any threads, nor is the moving element subjected to undue force by any of the adjustments made with the present invention.

Both large and extremely ne and accurate adjustments may be made very quickly, and will be maintained for a long period of time without necessity for readjustment. Counter-balance weights may be taken 01T the balance arms in a minimum amount of time and replaced with diiferent weights, without damage to the assembled instrument, and with a minimum amount of labor.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction setv forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In la counter-balance for the moving element of an instrument, the combination of a moving element provided with a balance arm, a counter-balance weight slidably mounted for longitudinal movement on said balance arm and having la helically extending groove in its external surface, and resilient means carried by the moving element and engaging in the groove of the counter-balance weight for holdingv said counterbalance Weight in any of a. multiplicity of different adjusted positions. Y

2. In a counter-balance for the moving element of an instrument, the combination of a moving element provided with a balance arm, a counterbalance weight' slidably mounted on said balance arm, and resilient means for holding said counter-balance-weight in any of .a multiplicity of diierent adjusted positions, said counter-balance weight being provided with external peripherally extending helical formations for engaging said resilient means, whereby rotation of the weight eects a ne adjustment ofthe Weight longitudinally of the'arm. 'L

3. In a counter-balance for the moving element of an instrument, the combination of a moving element provided with a balance arm and comprising a helically wound coil, a counterbalance weight slidably mounted on said balance arm, and resilient means for holding said counter-balance 'weight in any of a multiplicity of different adjusted positions, said counter-balance weight being provided along its length with a multiplicity" of depressions consisting of the grooves between successive turns of the coil and adapted to receive a complementary formation on said resilient means, whereby said resilient means may; be spread from the weight and the weight slidf. longitudinally of the arm to effect a quick longitudinal adjustment.

4. In a counter-balance for the moving element of aninstrument, the combination of a moving element provided with a balance arm, a counter-balance weight comprising a helically wound coilrslidably mounted for longitudinal -movement'foh said balance arm, and resilient means for holding said counter-balance weight in any of a multiplicity of diierent adjusted positions, said resilient means comprising a spring arm extending in the same general direction as the balanceklarm and having a laterally turned end portion'.V engaging the weight between the turns of said coil.

5. In a counter-balance for the moving element of an instrument, the combination of a moving element provided with a balance arm, a counterbalance weight comprising a helically wound coil slidably mounted for longitudinal movement on said balance.r arm, and resilient; means for holding said counter-balance weight in any of a multiplicity of `different adjusted positions, said resilient means comprising a spring arm extending in the same general direction as the balance arm and having a laterally turned end portion engaging the weight between the turns of said coil, said end portion being provided with a relatively sharp edge.

6. In a counter-balance for the moving element of--an instrument, the combination rof a moving elementl provided with a balance arm, a

Y counter-balance weight slidably mounted on said balancearm, and resilient means for holding said counter-balance Weight in any of a multiplicityv of different adjusted positions, said resilient means comprising a spring arm separate from themweight and carried by the moving element and extending in the same general direction as'the balance arm and having a laterally turned end portion engaging the weight, said end portion being-provided with a relatively sharp edge, and said 'weight being formed with a multiplicity of transversely extending tapered depressions for receiving said sharp edge.

7. Ina'counter-balance for the moving element of. an instrument, the combination of a' moving element provided with a balance arm, a

counter-balance weight slidably mounted on said balance arm, and resilient means for holding said counter-balance weight in any of a multiplicity of diierent adjusted positions, said resilient means comprising .a spring arm extending in the same general direction as the balance arm and having a laterally turned end portion engaging the weight, said end portion being provided with -a relatively sharp edged engaging por'- tion for engaging the weight, and said weight being formed with helical guide formations for engaging said sharp edge whereby a close longitudinal adjustment of the Weight may be accomplished by rotating the weight with the weight engaging said sharp edge and said edge being guided by said helical formations to cause the weight to progress along the balance arm. f

9. In a counter-balance for the moving element of an instrument, the combination of a moving element provided with -a balance arm, a counter-balance weight slidably mounted on said balance arm, and resilient means for holding said counter-balance weight in any of a multiplicity of different adjusted positions, said resilient means comprising a spring arm extending in the same general direction as the balance arm and having a laterally turned end portion engaging the weight, said end Yportion being provided with a relatively sharp edged engaging portion for engaging the weight, and said weight being formed with helical guide formations for engaging said sharp edge whereby a close longitudinal adjustment of the weight may be accomplished by rotating th-e weight with the weight engaging said sharp edge and said edge being guided by said helica1 formations to cause the weight to progress along the' balance arm, said resilient Ameans being movable out of engagement with the counter-balance weight to permit removal, replacement, or coarse adjustment of the counterbalance weight.

10. In a counter-balanced moving element for instruments, the combination of a supporting body with pivots and bearings for supporting said body for pivotal movement, a needle-supporting arm carried by said body, and a balance arm carried `by said body, said balance arm being provided with a counter-balance weight having a bore for receiving the said balance arm and being mounted thereon for longitudinal sliding movement and for rotation, and resilient means carried by said body for engaging said counterbalance weight and holding it in any predetermined adjusted position, said weight having threaded engagement withsaid resilient means for fine longitudinal adjustment and being slidably free of said resilient means for coarse adjustment said resilient means including a spring metal body having -a resilient arm extending 10ngitudinally of said balance arm, and having a instruments, the combination of a supporting .body with pivots and bearings for supporting said body for pivotal movement, a needle-supporting arm carried by said body, and a balance arm carried by said body, said balance arm being provided with a counter-balance weight having a bore for receiving said arm and being mounted thereon for longitudinal sliding movement and for rotation, and resilient means carried by said body and having a sharpened end engaging between helically extending shoulders on said weight for engaging said counter-balance weight and .holding it in any predetermined adjusted position, said body also supporting a plurality of laterally extending balance arms provided with similar balance weights, and similar resilient means for securing them in adjusted position.

l2. In a counter-balanced moving element for instruments, the combination of a supporting body with pivots and bearings for supporting said body for pivotal movement, a needle-supporting arm carried by said body, and a balance arm carried by said body, said balance arm being provided with a counter-balance weight mounted thereon for longitudinal sliding movement and for rotation, and resilient means carried by said body for engaging said counter-balance weight and holding it in any predetermined adjusted position, said body also supporting a plurality of laterally extending balance arms provided with similar balance weights, and similar resilient means for securing them in adjusted position, the counterbalance weights being provided with helical guide surfaces for engaging said resilient means, whereby the rotation of the balance weights effects a close longitudinal adjustment of the weights on the balance arms. y

13. In a counter-balanced moving elementfor instruments, the combination of a supporting body with pivots and bearings for supporting said body for pivotal movement, a needle-supporting anncarried by said body, and a balance arm carried by said body, said balance arm being provided with a counter-balance weight mounted thereon for sliding movement .and for rotation, and resilient means carried by said body for engaging said counter-balance weight and holding it in any predetermined adjusted position, said resilient means including a spring metal body having a resilient arm extending longitudinally of said balance arm, and said resilient arms being downwardly turned and provided with relatively fine engaging edges for engaging the counter-balance weights.

14. In a counter-balance for the moving element of an instrument, the combination of a moving element provided with a balance arm, a

.counter-balance weight comprising a coil of sublstantially helical shape slidably mounted on said balance arm, and resilient means for holding said counter-balance weight in any of a multiplicity of dierent adjusted positions, said resilient means comprising a spring arm extending in the same general direction as the balance arm and having a laterally turned end portion engaging 1 the weight, said end portion being provided with 'a relatively sharp edged engaging portion for engaging the weight, said counter-balance arms being polygonal and of substantially the same dimension between its corners, whereby the cornersof the balance arm are adapted to guidethe counterweight and the counter-weight being provided with a substantially cylindrical bore.

15. In a counter-balance for the moving element of an instrument, the combination of Va. moving element provided with a balance arm, a counter-balance weight slidably mounted for longitudinal movement on said balance arm, and resilient means for holding said counter-balance weight in any of a multiplicity of different adjusted positions, said resilient means comprising a spring arm extending in the same general direction as the balance arm and having a laterally turned end portion engaging the weight, said end portion being provided with a relatively sharp .edged engaging portion for engaging the weight,

said counter-balance arms being polygonal and of substantially the same dimension between its corners, whereby the corners of the balance arm are adapted to guide the counter-weight and the counter-weight being provided with a substantially cylindrical bore, said counter-balance weight comprising a helical coil spring with its successive coils engaging each other.

16. In a counter balance for the moving element of an instrument or the like, the combination of a moving element with a balance arm, a counter balance weight comprising a member having abore adapted to receive said balance arm, whereby said weight is mounted on said balance arm for rotation and longitudinal sliding movement, said weight being formed about its periphery with a plurality of helical formations, and a securing member xedly secured to said moving element and having aportion engaging said helical formations, whereby the rotation of the weight on the balance arm causes the'weight to progress along the arm by virtue of the threadlike action of said helical formations on said engaging portion to eiect a ne adjustment in either diretion.

17. In a counter balance for the moving element of an instrument or the like, the combination of a moving element with a balance arm, a counter balance weight comprising a member having a bore adapted to receiveA said balance arm, whereby said weight is mounted on said balance arm for rotation and longitudinal sliding movement, said weight being formed about its periphery with a plurality of helical formations, and a securing member xedly secured to said moving element and having a portion engaging said helical formations, whereby the rotation of the weight on the balance arm causes the weight to progress along the arm by virtue of the threadlike action of said helical formations on said engaging portion to effect va ne adjustment in either direction, said weight comprising a closely wound helical coil,

18. In a counter balance for the moving element of an instrument or the like, the combination of a movingelement with a balance arm', a counter balance weight comprising a member having abore adapted to receive said balance arm, whereby said weight is mounted on said balance arm for rotation and sliding moving, said weight being formed aboutV its periphery with a plurality of helical formations, `and a securing member fixedly secured to said moving element and having a portion engaging said helical formations, whereby the rotation of the Weight on the balance arm causes the weight to progress alo-ng the arm by virtue of the thread-like action of said helical formations on said engaging portion to eiect a. iine adjustment in either direction, said member including a, resilient portion between said engaging portion and the point of UNITED STATES PATENTS securement of said member on said movement, Number Name Date whereby the engaging portion may be lifted from 611,722 Weston Och 4, 1393 the helical formations while the weight is slid 5 1,154,979 Ems Sept. 2g, 1915 bodily to effect a coarse adjustment. 1,579,349 Weston Apr 6J 1926 1,889,764 Stiokney Dec.6, 1932 RAY SIMPSON- 2,111,001 Norman Mai-.15,1938

FOREIGN PATENTS Country Date REFERENCES CITED lo The following references are of record in the le of this patent:

Number Germany July 19, 1939 

